Police submitted Rakib murder case charge-sheet on Sunday to a Khulna court accusing three persons of killing the boy.
Khulna Metropolitan Magistrate Faruq Iqbal accepted the charge-sheet submitted by Khulna Sadar thana SI and the IO of the case Kazi Mostak Ahmed.
The court also set September 22 as the next day of hearing.
Those who were charged with the murder are : Mohammed Sharif, owner of the workshop where Rakib worked, his mother Beauty Begum, and uncle Mintu Mia.
The 12-year old boy died on August 3 after a high-pressure air pump nozzle was inserted into his rectum and his body filled with air at a motorcycle repair shop, severely injuring his internal organs.